Chemicals That Mimic Hormones Spark Alarm and Debate

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IN a warning supported by allies who include Robert Redford and Vice President Al Gore, some environmentalists are asserting that humans and wildlife are facing a new and serious threat from synthetic chemicals.

These chemicals, they say, mimic natural hormones like estrogen and even in minute quantities can disrupt vital processes like fertility and fetal development. The so-called endocrine-disrupting chemicals are widespread in earth and water and, the environmentalists warn, may be wreaking many insidious forms of damage, like a decline in men's sperm counts, an epidemic of breast and prostate cancer, and fetal effects that emerge later as reduced intelligence, hyperactivity and violent behavior.

But issues like declining sperm counts are a matter of heated dispute among experts. [Page C10.]

The case against the endocrine-disrupting chemicals is made in a new book, "Our Stolen Future," written by Dr. Theo Colborn, a senior scientist at the World Wildlife Fund, Dianne Dumanoski, a reporter for The Boston Globe, and Dr. John Peterson Myers, director of the W. Alton Jones Foundation, an environmental group. The book is being heavily promoted by its publisher, Dutton of New York, and has received considerable attention.

But its message is controversial. Although some biologists agree that there is reason for concern about these chemicals, especially to certain populations of fish and birds, many others say there is no factual basis for the book's alarms, several of which have been refuted by careful studies.

The book comes with a Vice Presidential endorsement. In a foreword, Mr. Gore compares it with "Silent Spring," Rachel Carson's classic 1962 book that set off a movement to ban DDT and other pesticides. He describes the new book as "critically important," saying, "We must find out if there are ways to protect children, who appear to be at greatest risk for birth defects and developmental disorders from such hormonally active compounds."

Besides Mr. Gore's support, "Our Stolen Future" has been endorsed by several biologists and toxicologists who say that the book deserves to be heeded. In an interview, Dr. Colburn said she wanted to see the endocrine-disrupting chemicals phased out. These include DDT, still used abroad, and a wide variety of industrial chemicals like polychlorinated biphenyls, or PCB's, and other products used in plastics, detergents, spermicides and pesticides.

Her colleague, Dr. Myers, said the evidence was sufficient to press at least for a worldwide ban on DDT and further restrictions on PCB's. "As the science emerges and as public opinion begins to be manifest in consumer choices, we will see companies start to design things to eliminate these exposures," he said.

But several leading scientists view such positions as premature at best. They say that the case for ridding the world of these chemicals seems fueled more by hyperbole than facts and that many of the claims of demonstrable harm, when examined, turn out to be a house of cards.

These scientists say they are not arbitrarily dismissing fears that trace amounts of synthetic chemicals might injure people and wildlife. But, they say, there is a difference between a hypothesis and convincing evidence.

"It's hypothesis masked as fact," said Michael A. Gallo, a professor of toxicology at the Robert Wood Johnson Medical School in New Brunswick, N.J.

This assessment was also shared by Dr. Bruce Ames, a professor of biochemistry and molecular biology at the University of California at Berkeley. "It's a political movement and it's based on lousy science," said Dr. Ames, who was a member of a National Academy of Sciences panel that recently reported that pesticide residues in food were not an important cause of cancer.

Scientists agree that certain synthetic chemicals may mimic reproductive hormones. And, they say, there is no doubt that some of those chemicals, at certain times and places, have reached levels that adversely affect wildlife.

But, the question is, what, if any are the effects of minute amounts of these chemicals on humans? And that is where environmentalists like Dr. Colborn part company with many scientists.

One issue, scientists say, is that the amounts of the synthetic chemicals are so minuscule that they might be dwarfed by naturally occurring hormones in plants that have the same effects. Dr. Stephen Safe, a professor of toxicology at Texas A & M University, has calculated that synthetic chemicals contribute less than one one-thousandth of 1 percent of the amount of estrogenlike compounds that people consume in their diets.

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Dr. Colborn said people might have evolved so they could deal with the naturally occurring hormone disruptors but not with the synthetic ones. But others, including Dr. Delores Lamb, a hormone researcher at Baylor College of Medicine in Houston, said there was no evidence for that.

Dr. Colborn said she had stacks of scientific papers that taken together, told a convincing story about the dangers of synthetic endocrine-disrupting chemicals. "There are people who insist on direct cause-and-effect linkages," Dr. Colborn said. "But if these things can get to the embryo, you have to worry."

A prime exhibit in "Our Stolen Future" is the reported decline in human sperm counts. Another argument is that endocrine-disrupting chemicals could be causing an epidemic of breast cancer and prostate cancer. The National Cancer Institute is investigating the possibility that pesticides might increase the risk of these cancers in people exposed to high doses, like farmers and their wives, said Dr. Shelia Zahm, an epidemiologist at the institute.

But, Dr. Zahm added, even if high levels of pesticides should turn out to raise the risk of breast or prostate cancer, it does not necessarily follow that very low levels would also do so. And, she said, the epidemic of prostate cancer is thought to be a reporting effect, not a natural event, due to a new blood test that is detecting cancers that would otherwise have never been found. The Cancer Institute and the American Cancer Society have concluded that there is no breast cancer epidemic.

Asked for the strongest, most convincing evidence that endocrine disruptors are affecting humans, Dr. Colborn said it was studies indicating that these chemicals are causing hyperactivity in children. "The evidence is just building up," she said, citing animal studies.

She added that she also worried that endocrine-disrupting chemicals were causing a decline in intelligence and said that animal studies showed that such chemicals could weaken short-term memory in rodents.

"If you have problems with short-term memory, you have problems with intelligence," she said. "Remember, the thyroid fits in here," she said. "There are thyroid problems in practically every fish in the Great Lakes. And thyroidologists say that it takes just the slightest shift during critical times in the development of the brain and you will have behavioral problems and intelligence problems."

But Dr. Maria I. New, chief of pediatric endocrinology at New York Hospital-Cornell University Medical Center in New York, said there was no evidence that learning disabilities, violence or a drop in I.Q. had anything to do with prenatal exposure to estrogens or endocrine-disrupting chemicals.

Another possibility raised in the book is that endocrine-disrupting chemicals can cause parents to neglect or abuse their children.

"What about the breakdown of the family and frequent reports of child abuse and neglect?" the authors wrote. "If scientists have found evidence of careless parenting in contaminated bird colonies, do these chemicals have any role in similar phenomena among human parents? Reacting to reports of growing neglect and violence against children by their parents, some commentators have ventured that there must be something wrong with these people, some basic instincts seem to be missing."

Dr. Myers said: "Yes, it is scary. We thought long and hard about whether to engage the public in such discussions, but we thought ultimately we had no choice."

But Dr. Zahm of the cancer institute dismissed the argument that endocrine-disrupting chemicals in the environment could cause such a variety of ills as "a leap -- in the quantum category."

"We shouldn't go beyond what our data show," she added.

Correction: March 21, 1996

An article in Science Times on Tuesday about chemicals that mimic natural hormones misstated an affiliation of Dr. Bruce Ames of the University of California. He is a member of the Commission on Life Sciences of the National Academy of Sciences, which oversaw a recent report on pesticide residues in food; he was not a member of the panel that prepared the report.

A version of this article appears in print on March 19, 1996, on Page C00001 of the National edition with the headline: Chemicals That Mimic Hormones Spark Alarm and Debate. Order Reprints|Today's Paper|Subscribe